Method of forming metal shells and arbor for the saem



Feb. 24,1942; 1.. BRANNO N 'E-rAL 2,273,926

I METHOD OF FQRMING METAL-SHE LS AND ARBOR-FOR THE SAME Filed Dec.20,-1938 .2 Sheets-Sheet l I INVENTORS James ZmnnanJJlk/Mn/l. M/az n t ZATTORNEY Feb. 24; 1942. 2,273,926

METHOD OF FORMING METAL SHE/ILLS AND ARBOR FOR THE SAME J. 1.. BRANNONET AL Filed Dec. 20, 1958 2 Sheets-Sheet 2 INVENTORSJamaLmnnmFflzMem4Nmz v Ab lb UNITE D sTAr i Patented Feb. 24, 1942 hJames BrannonfPlalnfleld, and Stephen A. a

' Mraz, Perth Amboy, N. If, asslgnorl to Bakelite Corporation, acorporation of New Jersey Application ian, 1938, Serial No. 246,773

8' Claims. (or. 22-36) This invention relates toarbors or steel inastersandthe methodoi forming slush or lead,

articlestherefrom. i

The invention finds a more particular application "to? the preparationof molds into which liquid resins are poured and then hardened. The

molds are made of lead or type metal and'usually formed by dipping asteel master mold orarbor, a intoflthe metal while the latter is in amolten ,3 state whereupon themolten metal freezes or congeals thereon;the resulting layer of frozen metal is then stripped from the mastermold, as by Jarring "the'frozen metal mold looseirom the steel mastermold or jarbor; These casting molds are frequentlycalled. slush-molds. a1

As heretoforemade,"each-unit slush mold has comprised one or moreindividual molds andhas an upwardly flared ever flow chamberto-fa'cilqitate the pouring 'of resin into the individual molds. Theseover-flow chambers.) however,

vary in height and size Iand'h'ence can ,notfbe spilled overthe crimped,edges. Usually, the resin has been firstjpouredinio a ladle and thenfrom the, ladle into the over-flow chamber of each unit slush orcastingmold; j This not only has necessitated considerablemanual workbut also;

t has occ'asi'oned considerable delay during which theliquidresin hascooled'and thickened, and H the pouring operation has thus been renderedincreasingly difficult. Furthermore, as the resin cooled: it hasincreased in viscosity and any bubbles. infthe individualmolds havethereafter been removed with difficulty, if at all. Finally, aftercuring each cast article has hadto be knocked out of its individual moldseparately, because the irregulariyshaped over-flow chambers haveresulted in unit molds not ea'sily centered or knocked out byonestrokeofa' punch-pre P vided with gang knock-out dies.

The principle upon which based lsthe failure of molten low melting pointmetals to freeze on'sharp edges of steel arbors which' are dippedthe'rein.' This is attributable to the'rapidity'withwhich such sharpedges become heated to the temperature of the molten metalyedgesyofthis. character are bounded by surfaces that meat an acute anglefi; e.materially less' than 90- degress with each other or are relativelycloseutogether to give a thin structure of the nature ofa wedge orstrip.

Briefly, the invention providesan arbor having a backing'plate providedon its edge with av wedge shaped skirt having a sharp knife orIsev--ering edge along its bottom; this skirt is adapted to hang downa shortdistance around the flngers of the arbor. Venting holes'or slots areprovided in the backing plate or, preferably, extend laterally throughthe skirt for discharging gases entrapped thereunder; this allows themolten lead tofrun ,up under the skirt.

The foregoing, as well as other and further ad- I vantages and objectswill be readily understood by referring to the following description andmore particularly to the drawings which illustrate a specific embodimentof this invention and wherein:

ure 1 is a lateral view of an arbor, h g

a portion of a lead shell or unit casting mold formed on the right handportion of the arbor, the :left portion of the lead shell being cut awayin order to show the construction of the arbor;

, Figure 2 is a vertical sectonal view of the arbor and lead shell moldshowing the'skirt and venting holes;

Figure 3 isa perspective view of a number of I lead shell or unit,casting moldsstacked or groupedfor the resin pouring or castingstep;

Figure 4 is a perspective view partially in verticalysection of the unitcasting mold shown in positioned an arborpressfltted with a com positeor gang knock-outdie. 1

The present, invention overcomes these and otherdifflcultles which haveheretofore handicapped the cast .resinindustry, by providing ,animproved arbor for :making unit slush molds which are uniform in sizeand thus can bereadily stacked or grouped and hand ed inautomatic orsemi-automatic machinery; all the resin articles castandhardenedin sucha unit mold can be Fig. -1, after the arbor has been withdrawn and,

resin articles have been cast and hardened in the individual moldcavities of the lead shell; and Figure 5 is a cornerportion ofa modifiedarbor.

Referring now in more detail to the drawings, an arborFlg. 1, comprisesa handle I I, an insulating sheath l2, and abacking plate It havingmounted on its lower surface a number of fingers i4 and, having on itssides a wedge shaped skirt portion 15 with aknife edge 16. Ventingholes-- I! in the backing plate, or preferably as at-I8 in v n theskirt, are provided fordischarging gases en- I this invention 1 istrapped under the skirt I! thus enabling the molten lead to run up underthe skirt.

When dipped into molten lead, a lead shell or casting form 20 freezesand hardens conformably over the fingers l4 and heavy portions of thearbor; relatively little if any lead freezes on the sharp edge It. Thelayer of metal 2| which forms on the outside of skirt l5 falls of! uponwithdrawalof the arbor from the molten bath or drops off when the steelarbor is freed from its lead shell during, the arbor stripping orjarring step. This outside strip of metal 2| is usually the first partto be jarred loose, and is easily removed because the molten leaddoesnot freeze on or across the sharp knife edge It and hence no supportis left for strip 2| once-it is Jarred loose from skirt portion l5.Further jarring of the lead mold and arbor assembly serves to separatethe lead mold from the arbor, leaving a lead mold having a flat top 22and straight parallel sides 23 extending a shortdistance down from thetop 22; lead molds formed in this way are all uniform in size and shapeand hence can be in one operation and thereby eliminates the tedious andtime consuming process heretofore used wherein each article has beenknocked out individually by hand or with the aid of a pneumatic hammer.

What is claimed is:

1. Arbor for immersion into molten material for the freezing thereon ofa shell of the material comprising'in combination a dipping member, aplate extending transversely of the direction of dipping and from whichthe member projects, means associated therewith for delimiting thesurface upon which a continuous shell freezes, said means comprising askirt bounded stacked or grouped together like paving blocks,

shown at H, since the lead lugs left by the latter must be cut offbefore the molds can be stacked; but with the vents l8 .which passthrough the skirts l5, the lugs are cut off simultaneously with thestripping of the lead shell from the arbor.

' After the lead shell or casting forms 20, Fig. 4, are filled. with theviscous resin'they are stoved and heated at such a temperature and forsuch a period of time that the resin sets or curves to a permanentlyhardened state; then the hardened cast articles such as 25, Fig. 3, areremoved by knocking against the bottom of the lead molds with a hammer,air gun, punch press or the like.

The modification of the arbor shown in Fig. 5 includes a built up corner26 which forms a sharp edge 21. whereon little if any lead freezes.

facilitates the removal of the St i particularly where long moldcavities are made.

This results in a splitting of the strip 2| and thus and meansassociated, therewith for delimiting.

This type of mold effects a considerable saving in casting time, as theresin can be discharged on the surface 22 directly from the still andwhile it is hot and thus has a very low viscosity; this helpsconsiderably in eliminating air bubbles. Also, with the elimination ofthe individual over-flow chambers and with the introduction of thescraping step, excess resin heretofore left in the over-flow chambers isremoved and used in the cast and hardened articles. Thus, the resinwaste is largely eliminated and with large composite molds, the castingprocess becomes semi-automatic. Furthermore, because of the uniformityin size and contour of the. contiguous sides of the unit molds verylittle or no resin runs down between the contiguous sides 23 of themolds. This uniformity of size also makes possible the use of automaticmachinery for knocking out the contents of an entire unit mold bysurfaces relatively close together in acute angular relationship to eachother extending from the plate in the same. direction and about themember, and a vent'for releasing gases entrapped between the skirt andthe member.

2. Arbor for immersion into molten material for the freezing thereon ofa shell of the material comprising in combination a clipping member, aplate extending transversely of the direction of dipping and from whichthe member projects, and means associated therewith for delimiting thesurface upon which a continuous shell freezes, said means comprising askirt bounded by surfaces relatively close together in an acute angularrelationship to each other extending from the plate in the samedirection and about the member.

3. Arbor for immersion into molten material for the freezing thereon ofa shell of the material comprising in combination a dipping member, aplate extending transversely of the direction of dipping and from whichthe member projects.

the surface upon which a continuous shell freezes said means including askirt bounded by surfaces relatively close together in an acute angularrelationship to each other extending from the plate-in the samedirection and about the member and providing an interior wallfordefining a bounding surface of a shell formed on the arbor.

4. Arbor for immersion into molten material for the freezing thereon ofa shell of the material comprising in combination a dipping meme ber,and a plate extending transversely of the direction of dipping and fromwhich the member projects, said plate having a peripheral skirt boundedby surfaces relatively close together in an acute angular relationshipto each other for delimiting the surface upon which a continuous shellfreezes.

5. Arbor for immersion into molten material for the freezing thereon ofa shell of the material comprising a dipping member having a peripheralstrip bounded by surfaces relatively close together in an acute angularrelationship to each other associated therewith for delimiting thesurface upon which a continuous shell freezes.

6. In a method of forming a shell by the dipping of an arbor in a moltenmaterial and the freezing of the material thereon, the steps whichcomprise delimiting the surface of the arbor covered by the shell, andcausing separation of an excess formed in extension of the shell on thebounding comprise delimiting the surface of the arbor mar/seas 3 coveredby the shell by a surface transverse to the direction of dipping, andcausing sepatetlon of an excess formed ln extension of the shell on thearbor by preventinglreezlm along the boundlng' edge of the transversesurface.

8. In a method of forming a shell by the freezlng of molten metal on anarbor, the steps which comprise dipping" a relatively cold arbor in themolten metal to freeze a shell of the metal thereon, and dellmltlng theextent of e the shell so formed by a heetlnz locallzed and sufllclent to5 prevent freezln: at the boundary.

JAMES L. BRANNON. STEPHEN A. MRAZ.

